Characterization of thermostable alkaline protease from Bacillus halodurans SE5 and its application in degumming coupled with sericin hydrolysate production from yellow cocoon

Metagenomic and proteomic analysis of bacterial retting community and proteome profile in the degumming process of kenaf bast

BACKGROUND

Data on the microbial community and functional proteins associated with degumming in kenaf remains scant. Here, we analyzed the microbial communities associated with kenaf (Hibiscus cannabinus) bast fibers during retting to identify potential candidate degumming bacteria. Retting liquids were collected and analyzed at 0 days, 10 days, and 34 days and then evaluated the yield and quality of kenaf fiber at the different retting times. Besides, the microbial communities were characterized using metagenomic and proteomic analysis by LC-MS/MS technology.

RESULTS

The data showed that increase in the retting time significantly improves the softness, dispersion, and fiber whiteness of the kenaf fiber. The relative abundance of Acinetobacter increased from 2.88% at the baseline to 6.64% at the 34th retting. On the other hand, some members of Clostridium were reduced from 3% at the baseline to 2% at the 34th retting. Analysis of carbohydrate active enzymes showed constant changes in the utilization of carbohydrates. Besides, benzoquinone reductase, cellobiose dehydrogenase, glucose 1-oxidase, aryl alcohol oxidase and alcohol oxidase were the top five most abundant enzymes in the retting liquids. This present results demonstrated that the expressions of B7GYR8, Q6RYW5 and Q6FFK2 proteins were suppressed in Acinetobacter with the retting time. On the contrary, P05149 was upregulated with the retting time. In Clostridium, P37698, P52040 and P54937 proteins were upregulated with the retting time.

CONCLUSION

In addition, bacteria Acinetobacter and Clostridium might be playing important roles in the kenaf degumming process. Similarly, up-regulation of P37698, P52040 and P54937 proteins is an important manifestation and mediates important roles in the degumming process.

Factors affecting sericin hydrolysis and application of sericin hydrolysate in sericin films

Sericin is a natural protein and a by-product obtained from silk processing. To enhance the antioxidant properties of sericin, sericin hydrolysis was studied. The solvent effects (distilled water, citric acid and hydrochloric acid) and hydrolysis methods (heat treatment (water bath) and mild ultrasonic treatment at 20%, 40% or 60% amplitude) were investigated on the properties of sericin hydrolysate (SH). Furthermore, solvent effects (distilled water and 15% ethanol) were examined for the properties of the sericin films incorporated with selected SH. The SH samples from acid hydrolysis and the ultrasonic method had a darkened visual appearance. However, the degree of hydrolysis and antioxidant activity of SH increased with ultrasonic-assisted acid hydrolysis. The molecular weight (MW) of sericin was notably reduced. As expected, hydrochloric acid hydrolysis resulted in a lower MW for the SH than from citric acid. Thus, SH from hydrochloric acid and 20% amplitude in the ultrasonic method were selected to produce a sericin film. As revealed, using distilled water as a general solvent provided films with lower solubility and water vapor permeability but higher tensile strength. Furthermore, the addition of SH enhanced the antioxidant properties of its hydrolysate as a novel protein packaging film material for various applications.

Sericin cocoon bio-compatibilizer for reactive blending of thermoplastic cassava starch

Cassava starch was blended with glycerol to prepare thermoplastic starch (TPS). Thermoplastic starch was premixed with sericin (TPSS) by solution mixing and then melt-blended with polyethylene grafted maleic anhydride (PEMAH). The effect of sericin on the mechanical properties, morphology, thermal properties, rheology, and reaction mechanism was investigated. The tensile strength and elongation at break of the TPSS10/PEMAH blend were improved to 12.2 MPa and 100.4%, respectively. The TPS/PEMAH morphology presented polyethylene grafted maleic anhydride particles (2 μm) dispersed in the thermoplastic starch matrix, which decreased in size to approximately 200 nm when 5% sericin was used. The melting temperature of polyethylene grafted maleic anhydride (121 °C) decreased to 111 °C because of the small crystal size of the polyethylene grafted maleic anhydride phase. The viscosity of TPS/PEMAH increased with increasing sericin content because of the chain extension. Fourier-transform infrared spectroscopy confirmed the reaction between the amino groups of sericin and the maleic anhydride groups of polyethylene grafted maleic anhydride. This reaction reduced the interfacial tension between thermoplastic starch and polyethylene grafted maleic anhydride, which improved the compatibility, mechanical properties, and morphology of the blend.

Amino Acid Profile and Biological Properties of Silk Cocoon as Affected by Water and Enzyme Extraction

We compared the efficacy for protein extraction of water versus enzymatic extraction. The amino-acid composition, inhibitory activity against enzymes α-amylase and α-glucosidase, and anti-glycation activities of silk protein extract (SPE) were determined. We used water extraction (100 °C, six hours) and protease-enzymatic extraction. The microstructure of silk fibers was obviously different after extraction. The results showed that enzymatic extraction gave the greater values of protein content, amino acids, total phenolic content (TPC), and total flavonoid content (TFC), as well as all biological activities parameters tested, but it also provided a more bitter taste in the extract-contributing amino acids of 51% (arginine, phenylalanine, histidine, valine, tryptophan, isoleucine, and leucine) and less sweet and umami taste contributing amino acids than did water extraction, which could be more suitable to be used as concentrated nutraceuticals.

Extraction and antioxidant activity of sericin, a protein from silk

Abstract Sericin is a globular protein that represents 20% to 30% of the silk fiber from Bombyx mori silkworm cocoon. This protein is usually removed from the raw fiber and discarded by silk producers, a process known as degumming. However, sericin possesses significant biological properties that allows its application in various fields. The antioxidant activity is one of its most relevant benefits. Several authors have reported its anti-tyrosinase activity, lipid peroxidation inhibition and free radical neutralization. The antioxidant potential of sericin protein varies according to the extraction method used. Even though a wide variety of extraction techniques have been studied, simple technics including water at high temperature have exhibited efficient results. Furthermore, this method does not interfere with the safety of sericin for subsequent applications in food.